1 /*
   2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentG1Refine.hpp"
  27 #include "gc/g1/concurrentMark.hpp"
  28 #include "gc/g1/concurrentMarkThread.inline.hpp"
  29 #include "gc/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc/g1/g1CollectorPolicy.hpp"
  31 #include "gc/g1/g1IHOPControl.hpp"
  32 #include "gc/g1/g1GCPhaseTimes.hpp"
  33 #include "gc/g1/heapRegion.inline.hpp"
  34 #include "gc/g1/heapRegionRemSet.hpp"
  35 #include "gc/shared/gcPolicyCounters.hpp"
  36 #include "runtime/arguments.hpp"
  37 #include "runtime/java.hpp"
  38 #include "runtime/mutexLocker.hpp"
  39 #include "utilities/debug.hpp"
  40 #include "utilities/pair.hpp"
  41 
  42 // Different defaults for different number of GC threads
  43 // They were chosen by running GCOld and SPECjbb on debris with different
  44 //   numbers of GC threads and choosing them based on the results
  45 
  46 // all the same
  47 static double rs_length_diff_defaults[] = {
  48   0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  49 };
  50 
  51 static double cost_per_card_ms_defaults[] = {
  52   0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
  53 };
  54 
  55 // all the same
  56 static double young_cards_per_entry_ratio_defaults[] = {
  57   1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
  58 };
  59 
  60 static double cost_per_entry_ms_defaults[] = {
  61   0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
  62 };
  63 
  64 static double cost_per_byte_ms_defaults[] = {
  65   0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
  66 };
  67 
  68 // these should be pretty consistent
  69 static double constant_other_time_ms_defaults[] = {
  70   5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
  71 };
  72 
  73 
  74 static double young_other_cost_per_region_ms_defaults[] = {
  75   0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
  76 };
  77 
  78 static double non_young_other_cost_per_region_ms_defaults[] = {
  79   1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
  80 };
  81 
  82 G1CollectorPolicy::G1CollectorPolicy() :
  83   _predictor(G1ConfidencePercent / 100.0),
  84   _parallel_gc_threads(ParallelGCThreads),
  85 
  86   _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  87   _stop_world_start(0.0),
  88 
  89   _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  90   _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  91 
  92   _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  93   _prev_collection_pause_end_ms(0.0),
  94   _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
  95   _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  96   _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
  97   _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  98   _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  99   _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 100   _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 101   _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 102   _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
 103   _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 104   _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 105   _non_young_other_cost_per_region_ms_seq(
 106                                          new TruncatedSeq(TruncatedSeqLength)),
 107 
 108   _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
 109   _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
 110 
 111   _pause_time_target_ms((double) MaxGCPauseMillis),
 112 
 113   _recent_prev_end_times_for_all_gcs_sec(
 114                                 new TruncatedSeq(NumPrevPausesForHeuristics)),
 115 
 116   _recent_avg_pause_time_ratio(0.0),
 117   _rs_lengths_prediction(0),
 118   _max_survivor_regions(0),
 119 
 120   _eden_used_bytes_before_gc(0),
 121   _survivor_used_bytes_before_gc(0),
 122   _old_used_bytes_before_gc(0),
 123   _humongous_used_bytes_before_gc(0),
 124   _heap_used_bytes_before_gc(0),
 125   _metaspace_used_bytes_before_gc(0),
 126   _eden_capacity_bytes_before_gc(0),
 127   _heap_capacity_bytes_before_gc(0),
 128 
 129   _eden_cset_region_length(0),
 130   _survivor_cset_region_length(0),
 131   _old_cset_region_length(0),
 132 
 133   _collection_set(NULL),
 134   _collection_set_bytes_used_before(0),
 135 
 136   // Incremental CSet attributes
 137   _inc_cset_build_state(Inactive),
 138   _inc_cset_head(NULL),
 139   _inc_cset_tail(NULL),
 140   _inc_cset_bytes_used_before(0),
 141   _inc_cset_max_finger(NULL),
 142   _inc_cset_recorded_rs_lengths(0),
 143   _inc_cset_recorded_rs_lengths_diffs(0),
 144   _inc_cset_predicted_elapsed_time_ms(0.0),
 145   _inc_cset_predicted_elapsed_time_ms_diffs(0.0),
 146 
 147   // add here any more surv rate groups
 148   _recorded_survivor_regions(0),
 149   _recorded_survivor_head(NULL),
 150   _recorded_survivor_tail(NULL),
 151   _survivors_age_table(true),
 152 
 153   _gc_overhead_perc(0.0),
 154 
 155   _bytes_allocated_in_old_since_last_gc(0),
 156   _ihop_control(NULL),
 157   _initial_mark_to_mixed() {
 158 
 159   // SurvRateGroups below must be initialized after the predictor because they
 160   // indirectly use it through this object passed to their constructor.
 161   _short_lived_surv_rate_group =
 162     new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
 163   _survivor_surv_rate_group =
 164     new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
 165 
 166   // Set up the region size and associated fields. Given that the
 167   // policy is created before the heap, we have to set this up here,
 168   // so it's done as soon as possible.
 169 
 170   // It would have been natural to pass initial_heap_byte_size() and
 171   // max_heap_byte_size() to setup_heap_region_size() but those have
 172   // not been set up at this point since they should be aligned with
 173   // the region size. So, there is a circular dependency here. We base
 174   // the region size on the heap size, but the heap size should be
 175   // aligned with the region size. To get around this we use the
 176   // unaligned values for the heap.
 177   HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
 178   HeapRegionRemSet::setup_remset_size();
 179 
 180   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
 181   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
 182   clear_ratio_check_data();
 183 
 184   _phase_times = new G1GCPhaseTimes(_parallel_gc_threads);
 185 
 186   int index = MIN2(_parallel_gc_threads - 1, 7);
 187 
 188   _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
 189   _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
 190   _cost_scan_hcc_seq->add(0.0);
 191   _young_cards_per_entry_ratio_seq->add(
 192                                   young_cards_per_entry_ratio_defaults[index]);
 193   _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
 194   _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
 195   _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
 196   _young_other_cost_per_region_ms_seq->add(
 197                                young_other_cost_per_region_ms_defaults[index]);
 198   _non_young_other_cost_per_region_ms_seq->add(
 199                            non_young_other_cost_per_region_ms_defaults[index]);
 200 
 201   // Below, we might need to calculate the pause time target based on
 202   // the pause interval. When we do so we are going to give G1 maximum
 203   // flexibility and allow it to do pauses when it needs to. So, we'll
 204   // arrange that the pause interval to be pause time target + 1 to
 205   // ensure that a) the pause time target is maximized with respect to
 206   // the pause interval and b) we maintain the invariant that pause
 207   // time target < pause interval. If the user does not want this
 208   // maximum flexibility, they will have to set the pause interval
 209   // explicitly.
 210 
 211   // First make sure that, if either parameter is set, its value is
 212   // reasonable.
 213   if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 214     if (MaxGCPauseMillis < 1) {
 215       vm_exit_during_initialization("MaxGCPauseMillis should be "
 216                                     "greater than 0");
 217     }
 218   }
 219   if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 220     if (GCPauseIntervalMillis < 1) {
 221       vm_exit_during_initialization("GCPauseIntervalMillis should be "
 222                                     "greater than 0");
 223     }
 224   }
 225 
 226   // Then, if the pause time target parameter was not set, set it to
 227   // the default value.
 228   if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 229     if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 230       // The default pause time target in G1 is 200ms
 231       FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
 232     } else {
 233       // We do not allow the pause interval to be set without the
 234       // pause time target
 235       vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
 236                                     "without setting MaxGCPauseMillis");
 237     }
 238   }
 239 
 240   // Then, if the interval parameter was not set, set it according to
 241   // the pause time target (this will also deal with the case when the
 242   // pause time target is the default value).
 243   if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 244     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
 245   }
 246 
 247   // Finally, make sure that the two parameters are consistent.
 248   if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
 249     char buffer[256];
 250     jio_snprintf(buffer, 256,
 251                  "MaxGCPauseMillis (%u) should be less than "
 252                  "GCPauseIntervalMillis (%u)",
 253                  MaxGCPauseMillis, GCPauseIntervalMillis);
 254     vm_exit_during_initialization(buffer);
 255   }
 256 
 257   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
 258   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
 259   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
 260 
 261   // start conservatively (around 50ms is about right)
 262   _concurrent_mark_remark_times_ms->add(0.05);
 263   _concurrent_mark_cleanup_times_ms->add(0.20);
 264   _tenuring_threshold = MaxTenuringThreshold;
 265 
 266   assert(GCTimeRatio > 0,
 267          "we should have set it to a default value set_g1_gc_flags() "
 268          "if a user set it to 0");
 269   _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
 270 
 271   uintx reserve_perc = G1ReservePercent;
 272   // Put an artificial ceiling on this so that it's not set to a silly value.
 273   if (reserve_perc > 50) {
 274     reserve_perc = 50;
 275     warning("G1ReservePercent is set to a value that is too large, "
 276             "it's been updated to " UINTX_FORMAT, reserve_perc);
 277   }
 278   _reserve_factor = (double) reserve_perc / 100.0;
 279   // This will be set when the heap is expanded
 280   // for the first time during initialization.
 281   _reserve_regions = 0;
 282 
 283   _cset_chooser = new CollectionSetChooser();
 284 }
 285 
 286 G1CollectorPolicy::~G1CollectorPolicy() {
 287   delete _ihop_control;
 288 }
 289 
 290 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
 291   return _predictor.get_new_prediction(seq);
 292 }
 293 
 294 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
 295   return (size_t)get_new_prediction(seq);
 296 }
 297 
 298 void G1CollectorPolicy::initialize_alignments() {
 299   _space_alignment = HeapRegion::GrainBytes;
 300   size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
 301   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 302   _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
 303 }
 304 
 305 void G1CollectorPolicy::initialize_flags() {
 306   if (G1HeapRegionSize != HeapRegion::GrainBytes) {
 307     FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
 308   }
 309 
 310   if (SurvivorRatio < 1) {
 311     vm_exit_during_initialization("Invalid survivor ratio specified");
 312   }
 313   CollectorPolicy::initialize_flags();
 314   _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
 315 }
 316 
 317 void G1CollectorPolicy::post_heap_initialize() {
 318   uintx max_regions = G1CollectedHeap::heap()->max_regions();
 319   size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
 320   if (max_young_size != MaxNewSize) {
 321     FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
 322   }
 323 
 324   _ihop_control = create_ihop_control();
 325 }
 326 
 327 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
 328 
 329 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
 330         _min_desired_young_length(0), _max_desired_young_length(0) {
 331   if (FLAG_IS_CMDLINE(NewRatio)) {
 332     if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
 333       warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
 334     } else {
 335       _sizer_kind = SizerNewRatio;
 336       _adaptive_size = false;
 337       return;
 338     }
 339   }
 340 
 341   if (NewSize > MaxNewSize) {
 342     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 343       warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
 344               "A new max generation size of " SIZE_FORMAT "k will be used.",
 345               NewSize/K, MaxNewSize/K, NewSize/K);
 346     }
 347     MaxNewSize = NewSize;
 348   }
 349 
 350   if (FLAG_IS_CMDLINE(NewSize)) {
 351     _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
 352                                      1U);
 353     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 354       _max_desired_young_length =
 355                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 356                                   1U);
 357       _sizer_kind = SizerMaxAndNewSize;
 358       _adaptive_size = _min_desired_young_length == _max_desired_young_length;
 359     } else {
 360       _sizer_kind = SizerNewSizeOnly;
 361     }
 362   } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
 363     _max_desired_young_length =
 364                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 365                                   1U);
 366     _sizer_kind = SizerMaxNewSizeOnly;
 367   }
 368 }
 369 
 370 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
 371   uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
 372   return MAX2(1U, default_value);
 373 }
 374 
 375 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
 376   uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
 377   return MAX2(1U, default_value);
 378 }
 379 
 380 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
 381   assert(number_of_heap_regions > 0, "Heap must be initialized");
 382 
 383   switch (_sizer_kind) {
 384     case SizerDefaults:
 385       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 386       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 387       break;
 388     case SizerNewSizeOnly:
 389       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 390       *max_young_length = MAX2(*min_young_length, *max_young_length);
 391       break;
 392     case SizerMaxNewSizeOnly:
 393       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 394       *min_young_length = MIN2(*min_young_length, *max_young_length);
 395       break;
 396     case SizerMaxAndNewSize:
 397       // Do nothing. Values set on the command line, don't update them at runtime.
 398       break;
 399     case SizerNewRatio:
 400       *min_young_length = number_of_heap_regions / (NewRatio + 1);
 401       *max_young_length = *min_young_length;
 402       break;
 403     default:
 404       ShouldNotReachHere();
 405   }
 406 
 407   assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
 408 }
 409 
 410 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
 411   // We need to pass the desired values because recalculation may not update these
 412   // values in some cases.
 413   uint temp = _min_desired_young_length;
 414   uint result = _max_desired_young_length;
 415   recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
 416   return result;
 417 }
 418 
 419 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
 420   recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
 421           &_max_desired_young_length);
 422 }
 423 
 424 void G1CollectorPolicy::init() {
 425   // Set aside an initial future to_space.
 426   _g1 = G1CollectedHeap::heap();
 427 
 428   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 429 
 430   initialize_gc_policy_counters();
 431 
 432   if (adaptive_young_list_length()) {
 433     _young_list_fixed_length = 0;
 434   } else {
 435     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 436   }
 437   _free_regions_at_end_of_collection = _g1->num_free_regions();
 438 
 439   update_young_list_max_and_target_length();
 440   // We may immediately start allocating regions and placing them on the
 441   // collection set list. Initialize the per-collection set info
 442   start_incremental_cset_building();
 443 }
 444 
 445 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
 446   phase_times()->note_gc_start(num_active_workers);
 447 }
 448 
 449 // Create the jstat counters for the policy.
 450 void G1CollectorPolicy::initialize_gc_policy_counters() {
 451   _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
 452 }
 453 
 454 bool G1CollectorPolicy::predict_will_fit(uint young_length,
 455                                          double base_time_ms,
 456                                          uint base_free_regions,
 457                                          double target_pause_time_ms) const {
 458   if (young_length >= base_free_regions) {
 459     // end condition 1: not enough space for the young regions
 460     return false;
 461   }
 462 
 463   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 464   size_t bytes_to_copy =
 465                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 466   double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
 467   double young_other_time_ms = predict_young_other_time_ms(young_length);
 468   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 469   if (pause_time_ms > target_pause_time_ms) {
 470     // end condition 2: prediction is over the target pause time
 471     return false;
 472   }
 473 
 474   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
 475 
 476   // When copying, we will likely need more bytes free than is live in the region.
 477   // Add some safety margin to factor in the confidence of our guess, and the
 478   // natural expected waste.
 479   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 480   // of the calculation: the lower the confidence, the more headroom.
 481   // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 482   // copying due to anticipated waste in the PLABs.
 483   double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 484   size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 485 
 486   if (expected_bytes_to_copy > free_bytes) {
 487     // end condition 3: out-of-space
 488     return false;
 489   }
 490 
 491   // success!
 492   return true;
 493 }
 494 
 495 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
 496   // re-calculate the necessary reserve
 497   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 498   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 499   // smaller than 1.0) we'll get 1.
 500   _reserve_regions = (uint) ceil(reserve_regions_d);
 501 
 502   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 503 }
 504 
 505 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
 506                                                        uint base_min_length) const {
 507   uint desired_min_length = 0;
 508   if (adaptive_young_list_length()) {
 509     if (_alloc_rate_ms_seq->num() > 3) {
 510       double now_sec = os::elapsedTime();
 511       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 512       double alloc_rate_ms = predict_alloc_rate_ms();
 513       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 514     } else {
 515       // otherwise we don't have enough info to make the prediction
 516     }
 517   }
 518   desired_min_length += base_min_length;
 519   // make sure we don't go below any user-defined minimum bound
 520   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 521 }
 522 
 523 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
 524   // Here, we might want to also take into account any additional
 525   // constraints (i.e., user-defined minimum bound). Currently, we
 526   // effectively don't set this bound.
 527   return _young_gen_sizer->max_desired_young_length();
 528 }
 529 
 530 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
 531   return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq));
 532 }
 533 
 534 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
 535   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 536   update_max_gc_locker_expansion();
 537   return unbounded_target_length;
 538 }
 539 
 540 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
 541   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 542   _young_list_target_length = young_lengths.first;
 543   return young_lengths.second;
 544 }
 545 
 546 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
 547   YoungTargetLengths result;
 548 
 549   // Calculate the absolute and desired min bounds first.
 550 
 551   // This is how many young regions we already have (currently: the survivors).
 552   uint base_min_length = recorded_survivor_regions();
 553   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 554   // This is the absolute minimum young length. Ensure that we
 555   // will at least have one eden region available for allocation.
 556   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
 557   // If we shrank the young list target it should not shrink below the current size.
 558   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 559   // Calculate the absolute and desired max bounds.
 560 
 561   uint desired_max_length = calculate_young_list_desired_max_length();
 562 
 563   uint young_list_target_length = 0;
 564   if (adaptive_young_list_length()) {
 565     if (collector_state()->gcs_are_young()) {
 566       young_list_target_length =
 567                         calculate_young_list_target_length(rs_lengths,
 568                                                            base_min_length,
 569                                                            desired_min_length,
 570                                                            desired_max_length);
 571     } else {
 572       // Don't calculate anything and let the code below bound it to
 573       // the desired_min_length, i.e., do the next GC as soon as
 574       // possible to maximize how many old regions we can add to it.
 575     }
 576   } else {
 577     // The user asked for a fixed young gen so we'll fix the young gen
 578     // whether the next GC is young or mixed.
 579     young_list_target_length = _young_list_fixed_length;
 580   }
 581 
 582   result.second = young_list_target_length;
 583 
 584   // We will try our best not to "eat" into the reserve.
 585   uint absolute_max_length = 0;
 586   if (_free_regions_at_end_of_collection > _reserve_regions) {
 587     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 588   }
 589   if (desired_max_length > absolute_max_length) {
 590     desired_max_length = absolute_max_length;
 591   }
 592 
 593   // Make sure we don't go over the desired max length, nor under the
 594   // desired min length. In case they clash, desired_min_length wins
 595   // which is why that test is second.
 596   if (young_list_target_length > desired_max_length) {
 597     young_list_target_length = desired_max_length;
 598   }
 599   if (young_list_target_length < desired_min_length) {
 600     young_list_target_length = desired_min_length;
 601   }
 602 
 603   assert(young_list_target_length > recorded_survivor_regions(),
 604          "we should be able to allocate at least one eden region");
 605   assert(young_list_target_length >= absolute_min_length, "post-condition");
 606 
 607   result.first = young_list_target_length;
 608   return result;
 609 }
 610 
 611 uint
 612 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
 613                                                      uint base_min_length,
 614                                                      uint desired_min_length,
 615                                                      uint desired_max_length) const {
 616   assert(adaptive_young_list_length(), "pre-condition");
 617   assert(collector_state()->gcs_are_young(), "only call this for young GCs");
 618 
 619   // In case some edge-condition makes the desired max length too small...
 620   if (desired_max_length <= desired_min_length) {
 621     return desired_min_length;
 622   }
 623 
 624   // We'll adjust min_young_length and max_young_length not to include
 625   // the already allocated young regions (i.e., so they reflect the
 626   // min and max eden regions we'll allocate). The base_min_length
 627   // will be reflected in the predictions by the
 628   // survivor_regions_evac_time prediction.
 629   assert(desired_min_length > base_min_length, "invariant");
 630   uint min_young_length = desired_min_length - base_min_length;
 631   assert(desired_max_length > base_min_length, "invariant");
 632   uint max_young_length = desired_max_length - base_min_length;
 633 
 634   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 635   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 636   size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
 637   size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
 638   size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
 639   double base_time_ms =
 640     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 641     survivor_regions_evac_time;
 642   uint available_free_regions = _free_regions_at_end_of_collection;
 643   uint base_free_regions = 0;
 644   if (available_free_regions > _reserve_regions) {
 645     base_free_regions = available_free_regions - _reserve_regions;
 646   }
 647 
 648   // Here, we will make sure that the shortest young length that
 649   // makes sense fits within the target pause time.
 650 
 651   if (predict_will_fit(min_young_length, base_time_ms,
 652                        base_free_regions, target_pause_time_ms)) {
 653     // The shortest young length will fit into the target pause time;
 654     // we'll now check whether the absolute maximum number of young
 655     // regions will fit in the target pause time. If not, we'll do
 656     // a binary search between min_young_length and max_young_length.
 657     if (predict_will_fit(max_young_length, base_time_ms,
 658                          base_free_regions, target_pause_time_ms)) {
 659       // The maximum young length will fit into the target pause time.
 660       // We are done so set min young length to the maximum length (as
 661       // the result is assumed to be returned in min_young_length).
 662       min_young_length = max_young_length;
 663     } else {
 664       // The maximum possible number of young regions will not fit within
 665       // the target pause time so we'll search for the optimal
 666       // length. The loop invariants are:
 667       //
 668       // min_young_length < max_young_length
 669       // min_young_length is known to fit into the target pause time
 670       // max_young_length is known not to fit into the target pause time
 671       //
 672       // Going into the loop we know the above hold as we've just
 673       // checked them. Every time around the loop we check whether
 674       // the middle value between min_young_length and
 675       // max_young_length fits into the target pause time. If it
 676       // does, it becomes the new min. If it doesn't, it becomes
 677       // the new max. This way we maintain the loop invariants.
 678 
 679       assert(min_young_length < max_young_length, "invariant");
 680       uint diff = (max_young_length - min_young_length) / 2;
 681       while (diff > 0) {
 682         uint young_length = min_young_length + diff;
 683         if (predict_will_fit(young_length, base_time_ms,
 684                              base_free_regions, target_pause_time_ms)) {
 685           min_young_length = young_length;
 686         } else {
 687           max_young_length = young_length;
 688         }
 689         assert(min_young_length <  max_young_length, "invariant");
 690         diff = (max_young_length - min_young_length) / 2;
 691       }
 692       // The results is min_young_length which, according to the
 693       // loop invariants, should fit within the target pause time.
 694 
 695       // These are the post-conditions of the binary search above:
 696       assert(min_young_length < max_young_length,
 697              "otherwise we should have discovered that max_young_length "
 698              "fits into the pause target and not done the binary search");
 699       assert(predict_will_fit(min_young_length, base_time_ms,
 700                               base_free_regions, target_pause_time_ms),
 701              "min_young_length, the result of the binary search, should "
 702              "fit into the pause target");
 703       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 704                                base_free_regions, target_pause_time_ms),
 705              "min_young_length, the result of the binary search, should be "
 706              "optimal, so no larger length should fit into the pause target");
 707     }
 708   } else {
 709     // Even the minimum length doesn't fit into the pause time
 710     // target, return it as the result nevertheless.
 711   }
 712   return base_min_length + min_young_length;
 713 }
 714 
 715 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
 716   double survivor_regions_evac_time = 0.0;
 717   for (HeapRegion * r = _recorded_survivor_head;
 718        r != NULL && r != _recorded_survivor_tail->get_next_young_region();
 719        r = r->get_next_young_region()) {
 720     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
 721   }
 722   return survivor_regions_evac_time;
 723 }
 724 
 725 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
 726   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 727 
 728   size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
 729   if (rs_lengths > _rs_lengths_prediction) {
 730     // add 10% to avoid having to recalculate often
 731     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 732     update_rs_lengths_prediction(rs_lengths_prediction);
 733 
 734     update_young_list_max_and_target_length(rs_lengths_prediction);
 735   }
 736 }
 737 
 738 void G1CollectorPolicy::update_rs_lengths_prediction() {
 739   update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq));
 740 }
 741 
 742 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
 743   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
 744     _rs_lengths_prediction = prediction;
 745   }
 746 }
 747 
 748 HeapWord* G1CollectorPolicy::mem_allocate_work(size_t size,
 749                                                bool is_tlab,
 750                                                bool* gc_overhead_limit_was_exceeded) {
 751   guarantee(false, "Not using this policy feature yet.");
 752   return NULL;
 753 }
 754 
 755 // This method controls how a collector handles one or more
 756 // of its generations being fully allocated.
 757 HeapWord* G1CollectorPolicy::satisfy_failed_allocation(size_t size,
 758                                                        bool is_tlab) {
 759   guarantee(false, "Not using this policy feature yet.");
 760   return NULL;
 761 }
 762 
 763 
 764 #ifndef PRODUCT
 765 bool G1CollectorPolicy::verify_young_ages() {
 766   HeapRegion* head = _g1->young_list()->first_region();
 767   return
 768     verify_young_ages(head, _short_lived_surv_rate_group);
 769   // also call verify_young_ages on any additional surv rate groups
 770 }
 771 
 772 bool
 773 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
 774                                      SurvRateGroup *surv_rate_group) {
 775   guarantee( surv_rate_group != NULL, "pre-condition" );
 776 
 777   const char* name = surv_rate_group->name();
 778   bool ret = true;
 779   int prev_age = -1;
 780 
 781   for (HeapRegion* curr = head;
 782        curr != NULL;
 783        curr = curr->get_next_young_region()) {
 784     SurvRateGroup* group = curr->surv_rate_group();
 785     if (group == NULL && !curr->is_survivor()) {
 786       log_info(gc, verify)("## %s: encountered NULL surv_rate_group", name);
 787       ret = false;
 788     }
 789 
 790     if (surv_rate_group == group) {
 791       int age = curr->age_in_surv_rate_group();
 792 
 793       if (age < 0) {
 794         log_info(gc, verify)("## %s: encountered negative age", name);
 795         ret = false;
 796       }
 797 
 798       if (age <= prev_age) {
 799         log_info(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
 800         ret = false;
 801       }
 802       prev_age = age;
 803     }
 804   }
 805 
 806   return ret;
 807 }
 808 #endif // PRODUCT
 809 
 810 void G1CollectorPolicy::record_full_collection_start() {
 811   _full_collection_start_sec = os::elapsedTime();
 812   record_heap_size_info_at_start(true /* full */);
 813   // Release the future to-space so that it is available for compaction into.
 814   collector_state()->set_full_collection(true);
 815 }
 816 
 817 void G1CollectorPolicy::record_full_collection_end() {
 818   // Consider this like a collection pause for the purposes of allocation
 819   // since last pause.
 820   double end_sec = os::elapsedTime();
 821   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 822   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 823 
 824   _trace_old_gen_time_data.record_full_collection(full_gc_time_ms);
 825 
 826   update_recent_gc_times(end_sec, full_gc_time_ms);
 827 
 828   collector_state()->set_full_collection(false);
 829 
 830   // "Nuke" the heuristics that control the young/mixed GC
 831   // transitions and make sure we start with young GCs after the Full GC.
 832   collector_state()->set_gcs_are_young(true);
 833   collector_state()->set_last_young_gc(false);
 834   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 835   collector_state()->set_during_initial_mark_pause(false);
 836   collector_state()->set_in_marking_window(false);
 837   collector_state()->set_in_marking_window_im(false);
 838 
 839   _short_lived_surv_rate_group->start_adding_regions();
 840   // also call this on any additional surv rate groups
 841 
 842   record_survivor_regions(0, NULL, NULL);
 843 
 844   _free_regions_at_end_of_collection = _g1->num_free_regions();
 845   // Reset survivors SurvRateGroup.
 846   _survivor_surv_rate_group->reset();
 847   update_young_list_max_and_target_length();
 848   update_rs_lengths_prediction();
 849   cset_chooser()->clear();
 850 
 851   _bytes_allocated_in_old_since_last_gc = 0;
 852 
 853   record_pause(FullGC, _full_collection_start_sec, end_sec);
 854 }
 855 
 856 void G1CollectorPolicy::record_stop_world_start() {
 857   _stop_world_start = os::elapsedTime();
 858 }
 859 
 860 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
 861   // We only need to do this here as the policy will only be applied
 862   // to the GC we're about to start. so, no point is calculating this
 863   // every time we calculate / recalculate the target young length.
 864   update_survivors_policy();
 865 
 866   assert(_g1->used() == _g1->recalculate_used(),
 867          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 868          _g1->used(), _g1->recalculate_used());
 869 
 870   double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
 871   _trace_young_gen_time_data.record_start_collection(s_w_t_ms);
 872   _stop_world_start = 0.0;
 873 
 874   record_heap_size_info_at_start(false /* full */);
 875 
 876   phase_times()->record_cur_collection_start_sec(start_time_sec);
 877   _pending_cards = _g1->pending_card_num();
 878 
 879   _collection_set_bytes_used_before = 0;
 880   _bytes_copied_during_gc = 0;
 881 
 882   collector_state()->set_last_gc_was_young(false);
 883 
 884   // do that for any other surv rate groups
 885   _short_lived_surv_rate_group->stop_adding_regions();
 886   _survivors_age_table.clear();
 887 
 888   assert( verify_young_ages(), "region age verification" );
 889 }
 890 
 891 void G1CollectorPolicy::record_concurrent_mark_init_end(double
 892                                                    mark_init_elapsed_time_ms) {
 893   collector_state()->set_during_marking(true);
 894   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 895   collector_state()->set_during_initial_mark_pause(false);
 896 }
 897 
 898 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
 899   _mark_remark_start_sec = os::elapsedTime();
 900   collector_state()->set_during_marking(false);
 901 }
 902 
 903 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
 904   double end_time_sec = os::elapsedTime();
 905   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 906   _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
 907   _prev_collection_pause_end_ms += elapsed_time_ms;
 908 
 909   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 910 }
 911 
 912 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
 913   _mark_cleanup_start_sec = os::elapsedTime();
 914 }
 915 
 916 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
 917   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
 918                                                               "skip last young-only gc");
 919   collector_state()->set_last_young_gc(should_continue_with_reclaim);
 920   // We skip the marking phase.
 921   if (!should_continue_with_reclaim) {
 922     abort_time_to_mixed_tracking();
 923   }
 924   collector_state()->set_in_marking_window(false);
 925 }
 926 
 927 void G1CollectorPolicy::record_concurrent_pause() {
 928   if (_stop_world_start > 0.0) {
 929     double yield_ms = (os::elapsedTime() - _stop_world_start) * 1000.0;
 930     _trace_young_gen_time_data.record_yield_time(yield_ms);
 931   }
 932 }
 933 
 934 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 935   return phase_times()->average_time_ms(phase);
 936 }
 937 
 938 double G1CollectorPolicy::young_other_time_ms() const {
 939   return phase_times()->young_cset_choice_time_ms() +
 940          phase_times()->young_free_cset_time_ms();
 941 }
 942 
 943 double G1CollectorPolicy::non_young_other_time_ms() const {
 944   return phase_times()->non_young_cset_choice_time_ms() +
 945          phase_times()->non_young_free_cset_time_ms();
 946 
 947 }
 948 
 949 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
 950   return pause_time_ms -
 951          average_time_ms(G1GCPhaseTimes::UpdateRS) -
 952          average_time_ms(G1GCPhaseTimes::ScanRS) -
 953          average_time_ms(G1GCPhaseTimes::ObjCopy) -
 954          average_time_ms(G1GCPhaseTimes::Termination);
 955 }
 956 
 957 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
 958   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
 959 }
 960 
 961 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
 962   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
 963 }
 964 
 965 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 966   if (about_to_start_mixed_phase()) {
 967     return false;
 968   }
 969 
 970   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 971 
 972   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 973   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 974   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 975 
 976   bool result = false;
 977   if (marking_request_bytes > marking_initiating_used_threshold) {
 978     result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
 979     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 980                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 981                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
 982   }
 983 
 984   return result;
 985 }
 986 
 987 // Anything below that is considered to be zero
 988 #define MIN_TIMER_GRANULARITY 0.0000001
 989 
 990 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned) {
 991   double end_time_sec = os::elapsedTime();
 992 
 993   size_t cur_used_bytes = _g1->used();
 994   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
 995   bool last_pause_included_initial_mark = false;
 996   bool update_stats = !_g1->evacuation_failed();
 997 
 998   NOT_PRODUCT(_short_lived_surv_rate_group->print());
 999 
1000   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
1001 
1002   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
1003   if (last_pause_included_initial_mark) {
1004     record_concurrent_mark_init_end(0.0);
1005   } else {
1006     maybe_start_marking();
1007   }
1008 
1009   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
1010   if (app_time_ms < MIN_TIMER_GRANULARITY) {
1011     // This usually happens due to the timer not having the required
1012     // granularity. Some Linuxes are the usual culprits.
1013     // We'll just set it to something (arbitrarily) small.
1014     app_time_ms = 1.0;
1015   }
1016 
1017   if (update_stats) {
1018     _trace_young_gen_time_data.record_end_collection(pause_time_ms, phase_times());
1019     // We maintain the invariant that all objects allocated by mutator
1020     // threads will be allocated out of eden regions. So, we can use
1021     // the eden region number allocated since the previous GC to
1022     // calculate the application's allocate rate. The only exception
1023     // to that is humongous objects that are allocated separately. But
1024     // given that humongous object allocations do not really affect
1025     // either the pause's duration nor when the next pause will take
1026     // place we can safely ignore them here.
1027     uint regions_allocated = eden_cset_region_length();
1028     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
1029     _alloc_rate_ms_seq->add(alloc_rate_ms);
1030 
1031     double interval_ms =
1032       (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1033     update_recent_gc_times(end_time_sec, pause_time_ms);
1034     _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1035     if (recent_avg_pause_time_ratio() < 0.0 ||
1036         (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1037       // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1038       // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1039       if (_recent_avg_pause_time_ratio < 0.0) {
1040         _recent_avg_pause_time_ratio = 0.0;
1041       } else {
1042         assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1043         _recent_avg_pause_time_ratio = 1.0;
1044       }
1045     }
1046 
1047     // Compute the ratio of just this last pause time to the entire time range stored
1048     // in the vectors. Comparing this pause to the entire range, rather than only the
1049     // most recent interval, has the effect of smoothing over a possible transient 'burst'
1050     // of more frequent pauses that don't really reflect a change in heap occupancy.
1051     // This reduces the likelihood of a needless heap expansion being triggered.
1052     _last_pause_time_ratio =
1053       (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
1054   }
1055 
1056   bool new_in_marking_window = collector_state()->in_marking_window();
1057   bool new_in_marking_window_im = false;
1058   if (last_pause_included_initial_mark) {
1059     new_in_marking_window = true;
1060     new_in_marking_window_im = true;
1061   }
1062 
1063   if (collector_state()->last_young_gc()) {
1064     // This is supposed to to be the "last young GC" before we start
1065     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1066     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1067 
1068     if (next_gc_should_be_mixed("start mixed GCs",
1069                                 "do not start mixed GCs")) {
1070       collector_state()->set_gcs_are_young(false);
1071     } else {
1072       // We aborted the mixed GC phase early.
1073       abort_time_to_mixed_tracking();
1074     }
1075 
1076     collector_state()->set_last_young_gc(false);
1077   }
1078 
1079   if (!collector_state()->last_gc_was_young()) {
1080     // This is a mixed GC. Here we decide whether to continue doing
1081     // mixed GCs or not.
1082     if (!next_gc_should_be_mixed("continue mixed GCs",
1083                                  "do not continue mixed GCs")) {
1084       collector_state()->set_gcs_are_young(true);
1085 
1086       maybe_start_marking();
1087     }
1088   }
1089 
1090   _short_lived_surv_rate_group->start_adding_regions();
1091   // Do that for any other surv rate groups
1092 
1093   if (update_stats) {
1094     double cost_per_card_ms = 0.0;
1095     double cost_scan_hcc = average_time_ms(G1GCPhaseTimes::ScanHCC);
1096     if (_pending_cards > 0) {
1097       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - cost_scan_hcc) / (double) _pending_cards;
1098       _cost_per_card_ms_seq->add(cost_per_card_ms);
1099     }
1100     _cost_scan_hcc_seq->add(cost_scan_hcc);
1101 
1102     double cost_per_entry_ms = 0.0;
1103     if (cards_scanned > 10) {
1104       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1105       if (collector_state()->last_gc_was_young()) {
1106         _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1107       } else {
1108         _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1109       }
1110     }
1111 
1112     if (_max_rs_lengths > 0) {
1113       double cards_per_entry_ratio =
1114         (double) cards_scanned / (double) _max_rs_lengths;
1115       if (collector_state()->last_gc_was_young()) {
1116         _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1117       } else {
1118         _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1119       }
1120     }
1121 
1122     // This is defensive. For a while _max_rs_lengths could get
1123     // smaller than _recorded_rs_lengths which was causing
1124     // rs_length_diff to get very large and mess up the RSet length
1125     // predictions. The reason was unsafe concurrent updates to the
1126     // _inc_cset_recorded_rs_lengths field which the code below guards
1127     // against (see CR 7118202). This bug has now been fixed (see CR
1128     // 7119027). However, I'm still worried that
1129     // _inc_cset_recorded_rs_lengths might still end up somewhat
1130     // inaccurate. The concurrent refinement thread calculates an
1131     // RSet's length concurrently with other CR threads updating it
1132     // which might cause it to calculate the length incorrectly (if,
1133     // say, it's in mid-coarsening). So I'll leave in the defensive
1134     // conditional below just in case.
1135     size_t rs_length_diff = 0;
1136     if (_max_rs_lengths > _recorded_rs_lengths) {
1137       rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1138     }
1139     _rs_length_diff_seq->add((double) rs_length_diff);
1140 
1141     size_t freed_bytes = _heap_used_bytes_before_gc - cur_used_bytes;
1142     size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes;
1143     double cost_per_byte_ms = 0.0;
1144 
1145     if (copied_bytes > 0) {
1146       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1147       if (collector_state()->in_marking_window()) {
1148         _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1149       } else {
1150         _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1151       }
1152     }
1153 
1154     if (young_cset_region_length() > 0) {
1155       _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1156                                                young_cset_region_length());
1157     }
1158 
1159     if (old_cset_region_length() > 0) {
1160       _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1161                                                    old_cset_region_length());
1162     }
1163 
1164     _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1165 
1166     _pending_cards_seq->add((double) _pending_cards);
1167     _rs_lengths_seq->add((double) _max_rs_lengths);
1168   }
1169 
1170   collector_state()->set_in_marking_window(new_in_marking_window);
1171   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1172   _free_regions_at_end_of_collection = _g1->num_free_regions();
1173   // IHOP control wants to know the expected young gen length if it were not
1174   // restrained by the heap reserve. Using the actual length would make the
1175   // prediction too small and the limit the young gen every time we get to the
1176   // predicted target occupancy.
1177   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1178   update_rs_lengths_prediction();
1179 
1180   update_ihop_prediction(app_time_ms / 1000.0,
1181                          _bytes_allocated_in_old_since_last_gc,
1182                          last_unrestrained_young_length * HeapRegion::GrainBytes);
1183   _bytes_allocated_in_old_since_last_gc = 0;
1184 
1185   _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1186 
1187   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1188   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1189 
1190   double scan_hcc_time_ms = average_time_ms(G1GCPhaseTimes::ScanHCC);
1191 
1192   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1193     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1194                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1195                                 update_rs_time_goal_ms, scan_hcc_time_ms);
1196 
1197     update_rs_time_goal_ms = 0;
1198   } else {
1199     update_rs_time_goal_ms -= scan_hcc_time_ms;
1200   }
1201   adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1202                                phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1203                                update_rs_time_goal_ms);
1204 
1205   cset_chooser()->verify();
1206 }
1207 
1208 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1209   if (G1UseAdaptiveIHOP) {
1210     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1211                                      G1CollectedHeap::heap()->max_capacity(),
1212                                      &_predictor,
1213                                      G1ReservePercent,
1214                                      G1HeapWastePercent);
1215   } else {
1216     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1217                                    G1CollectedHeap::heap()->max_capacity());
1218   }
1219 }
1220 
1221 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1222                                                size_t mutator_alloc_bytes,
1223                                                size_t young_gen_size) {
1224   // Always try to update IHOP prediction. Even evacuation failures give information
1225   // about e.g. whether to start IHOP earlier next time.
1226 
1227   // Avoid using really small application times that might create samples with
1228   // very high or very low values. They may be caused by e.g. back-to-back gcs.
1229   double const min_valid_time = 1e-6;
1230 
1231   bool report = false;
1232 
1233   double marking_to_mixed_time = -1.0;
1234   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1235     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1236     assert(marking_to_mixed_time > 0.0,
1237            "Initial mark to mixed time must be larger than zero but is %.3f",
1238            marking_to_mixed_time);
1239     if (marking_to_mixed_time > min_valid_time) {
1240       _ihop_control->update_marking_length(marking_to_mixed_time);
1241       report = true;
1242     }
1243   }
1244 
1245   // As an approximation for the young gc promotion rates during marking we use
1246   // all of them. In many applications there are only a few if any young gcs during
1247   // marking, which makes any prediction useless. This increases the accuracy of the
1248   // prediction.
1249   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1250     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1251     report = true;
1252   }
1253 
1254   if (report) {
1255     report_ihop_statistics();
1256   }
1257 }
1258 
1259 void G1CollectorPolicy::report_ihop_statistics() {
1260   _ihop_control->print();
1261 }
1262 
1263 #define EXT_SIZE_FORMAT "%.1f%s"
1264 #define EXT_SIZE_PARAMS(bytes)                                  \
1265   byte_size_in_proper_unit((double)(bytes)),                    \
1266   proper_unit_for_byte_size((bytes))
1267 
1268 void G1CollectorPolicy::record_heap_size_info_at_start(bool full) {
1269   YoungList* young_list = _g1->young_list();
1270   _eden_used_bytes_before_gc = young_list->eden_used_bytes();
1271   _survivor_used_bytes_before_gc = young_list->survivor_used_bytes();
1272   _heap_capacity_bytes_before_gc = _g1->capacity();
1273   _old_used_bytes_before_gc = _g1->old_regions_count() * HeapRegion::GrainBytes;
1274   _humongous_used_bytes_before_gc = _g1->humongous_regions_count() * HeapRegion::GrainBytes;
1275   _heap_used_bytes_before_gc = _g1->used();
1276   _eden_capacity_bytes_before_gc = (_young_list_target_length * HeapRegion::GrainBytes) - _survivor_used_bytes_before_gc;
1277   _metaspace_used_bytes_before_gc = MetaspaceAux::used_bytes();
1278 }
1279 
1280 void G1CollectorPolicy::print_detailed_heap_transition() const {
1281   YoungList* young_list = _g1->young_list();
1282 
1283   size_t eden_used_bytes_after_gc = young_list->eden_used_bytes();
1284   size_t survivor_used_bytes_after_gc = young_list->survivor_used_bytes();
1285   size_t heap_used_bytes_after_gc = _g1->used();
1286   size_t old_used_bytes_after_gc = _g1->old_regions_count() * HeapRegion::GrainBytes;
1287   size_t humongous_used_bytes_after_gc = _g1->humongous_regions_count() * HeapRegion::GrainBytes;
1288 
1289   size_t heap_capacity_bytes_after_gc = _g1->capacity();
1290   size_t eden_capacity_bytes_after_gc =
1291     (_young_list_target_length * HeapRegion::GrainBytes) - survivor_used_bytes_after_gc;
1292   size_t survivor_capacity_bytes_after_gc = _max_survivor_regions * HeapRegion::GrainBytes;
1293 
1294   log_info(gc, heap)("Eden: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1295                      _eden_used_bytes_before_gc / K, eden_used_bytes_after_gc /K, eden_capacity_bytes_after_gc /K);
1296   log_info(gc, heap)("Survivor: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1297                      _survivor_used_bytes_before_gc / K, survivor_used_bytes_after_gc /K, survivor_capacity_bytes_after_gc /K);
1298   log_info(gc, heap)("Old: " SIZE_FORMAT "K->" SIZE_FORMAT "K",
1299                      _old_used_bytes_before_gc / K, old_used_bytes_after_gc /K);
1300   log_info(gc, heap)("Humongous: " SIZE_FORMAT "K->" SIZE_FORMAT "K",
1301                      _humongous_used_bytes_before_gc / K, humongous_used_bytes_after_gc /K);
1302 
1303   MetaspaceAux::print_metaspace_change(_metaspace_used_bytes_before_gc);
1304 }
1305 
1306 void G1CollectorPolicy::print_phases() {
1307   phase_times()->print();
1308 }
1309 
1310 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1311                                                      double update_rs_processed_buffers,
1312                                                      double goal_ms) {
1313   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1314   ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1315 
1316   if (G1UseAdaptiveConcRefinement) {
1317     const int k_gy = 3, k_gr = 6;
1318     const double inc_k = 1.1, dec_k = 0.9;
1319 
1320     int g = cg1r->green_zone();
1321     if (update_rs_time > goal_ms) {
1322       g = (int)(g * dec_k);  // Can become 0, that's OK. That would mean a mutator-only processing.
1323     } else {
1324       if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1325         g = (int)MAX2(g * inc_k, g + 1.0);
1326       }
1327     }
1328     // Change the refinement threads params
1329     cg1r->set_green_zone(g);
1330     cg1r->set_yellow_zone(g * k_gy);
1331     cg1r->set_red_zone(g * k_gr);
1332     cg1r->reinitialize_threads();
1333 
1334     int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1);
1335     int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1336                                     cg1r->yellow_zone());
1337     // Change the barrier params
1338     dcqs.set_process_completed_threshold(processing_threshold);
1339     dcqs.set_max_completed_queue(cg1r->red_zone());
1340   }
1341 
1342   int curr_queue_size = dcqs.completed_buffers_num();
1343   if (curr_queue_size >= cg1r->yellow_zone()) {
1344     dcqs.set_completed_queue_padding(curr_queue_size);
1345   } else {
1346     dcqs.set_completed_queue_padding(0);
1347   }
1348   dcqs.notify_if_necessary();
1349 }
1350 
1351 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1352   return get_new_size_prediction(_rs_length_diff_seq);
1353 }
1354 
1355 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1356   return get_new_prediction(_alloc_rate_ms_seq);
1357 }
1358 
1359 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1360   return get_new_prediction(_cost_per_card_ms_seq);
1361 }
1362 
1363 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1364   return get_new_prediction(_cost_scan_hcc_seq);
1365 }
1366 
1367 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1368   return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1369 }
1370 
1371 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1372   return get_new_prediction(_young_cards_per_entry_ratio_seq);
1373 }
1374 
1375 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1376   if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1377     return predict_young_cards_per_entry_ratio();
1378   } else {
1379     return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1380   }
1381 }
1382 
1383 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1384   return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1385 }
1386 
1387 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1388   return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1389 }
1390 
1391 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1392   if (collector_state()->gcs_are_young()) {
1393     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1394   } else {
1395     return predict_mixed_rs_scan_time_ms(card_num);
1396   }
1397 }
1398 
1399 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1400   if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1401     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1402   } else {
1403     return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1404   }
1405 }
1406 
1407 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1408   if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1409     return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1410   } else {
1411     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1412   }
1413 }
1414 
1415 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1416   if (collector_state()->during_concurrent_mark()) {
1417     return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1418   } else {
1419     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1420   }
1421 }
1422 
1423 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1424   return get_new_prediction(_constant_other_time_ms_seq);
1425 }
1426 
1427 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1428   return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1429 }
1430 
1431 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1432   return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1433 }
1434 
1435 double G1CollectorPolicy::predict_remark_time_ms() const {
1436   return get_new_prediction(_concurrent_mark_remark_times_ms);
1437 }
1438 
1439 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1440   return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1441 }
1442 
1443 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1444   TruncatedSeq* seq = surv_rate_group->get_seq(age);
1445   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1446   double pred = get_new_prediction(seq);
1447   if (pred > 1.0) {
1448     pred = 1.0;
1449   }
1450   return pred;
1451 }
1452 
1453 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1454   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1455 }
1456 
1457 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1458   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1459 }
1460 
1461 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1462                                                        size_t scanned_cards) const {
1463   return
1464     predict_rs_update_time_ms(pending_cards) +
1465     predict_rs_scan_time_ms(scanned_cards) +
1466     predict_constant_other_time_ms();
1467 }
1468 
1469 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1470   size_t rs_length = predict_rs_length_diff();
1471   size_t card_num;
1472   if (collector_state()->gcs_are_young()) {
1473     card_num = predict_young_card_num(rs_length);
1474   } else {
1475     card_num = predict_non_young_card_num(rs_length);
1476   }
1477   return predict_base_elapsed_time_ms(pending_cards, card_num);
1478 }
1479 
1480 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1481   size_t bytes_to_copy;
1482   if (hr->is_marked())
1483     bytes_to_copy = hr->max_live_bytes();
1484   else {
1485     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1486     int age = hr->age_in_surv_rate_group();
1487     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1488     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1489   }
1490   return bytes_to_copy;
1491 }
1492 
1493 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1494                                                          bool for_young_gc) const {
1495   size_t rs_length = hr->rem_set()->occupied();
1496   size_t card_num;
1497 
1498   // Predicting the number of cards is based on which type of GC
1499   // we're predicting for.
1500   if (for_young_gc) {
1501     card_num = predict_young_card_num(rs_length);
1502   } else {
1503     card_num = predict_non_young_card_num(rs_length);
1504   }
1505   size_t bytes_to_copy = predict_bytes_to_copy(hr);
1506 
1507   double region_elapsed_time_ms =
1508     predict_rs_scan_time_ms(card_num) +
1509     predict_object_copy_time_ms(bytes_to_copy);
1510 
1511   // The prediction of the "other" time for this region is based
1512   // upon the region type and NOT the GC type.
1513   if (hr->is_young()) {
1514     region_elapsed_time_ms += predict_young_other_time_ms(1);
1515   } else {
1516     region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1517   }
1518   return region_elapsed_time_ms;
1519 }
1520 
1521 void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1522                                                  uint survivor_cset_region_length) {
1523   _eden_cset_region_length     = eden_cset_region_length;
1524   _survivor_cset_region_length = survivor_cset_region_length;
1525   _old_cset_region_length      = 0;
1526 }
1527 
1528 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1529   _recorded_rs_lengths = rs_lengths;
1530 }
1531 
1532 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1533                                                double elapsed_ms) {
1534   _recent_gc_times_ms->add(elapsed_ms);
1535   _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1536   _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1537 }
1538 
1539 void G1CollectorPolicy::clear_ratio_check_data() {
1540   _ratio_over_threshold_count = 0;
1541   _ratio_over_threshold_sum = 0.0;
1542   _pauses_since_start = 0;
1543 }
1544 
1545 size_t G1CollectorPolicy::expansion_amount() {
1546   double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1547   double last_gc_overhead = _last_pause_time_ratio * 100.0;
1548   double threshold = _gc_overhead_perc;
1549   size_t expand_bytes = 0;
1550 
1551   // If the heap is at less than half its maximum size, scale the threshold down,
1552   // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1553   // though the scaling code will likely keep the increase small.
1554   if (_g1->capacity() <= _g1->max_capacity() / 2) {
1555     threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1556     threshold = MAX2(threshold, 1.0);
1557   }
1558 
1559   // If the last GC time ratio is over the threshold, increment the count of
1560   // times it has been exceeded, and add this ratio to the sum of exceeded
1561   // ratios.
1562   if (last_gc_overhead > threshold) {
1563     _ratio_over_threshold_count++;
1564     _ratio_over_threshold_sum += last_gc_overhead;
1565   }
1566 
1567   // Check if we've had enough GC time ratio checks that were over the
1568   // threshold to trigger an expansion. We'll also expand if we've
1569   // reached the end of the history buffer and the average of all entries
1570   // is still over the threshold. This indicates a smaller number of GCs were
1571   // long enough to make the average exceed the threshold.
1572   bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1573   if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1574       (filled_history_buffer && (recent_gc_overhead > threshold))) {
1575     size_t min_expand_bytes = HeapRegion::GrainBytes;
1576     size_t reserved_bytes = _g1->max_capacity();
1577     size_t committed_bytes = _g1->capacity();
1578     size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1579     size_t expand_bytes_via_pct =
1580       uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1581     double scale_factor = 1.0;
1582 
1583     // If the current size is less than 1/4 of the Initial heap size, expand
1584     // by half of the delta between the current and Initial sizes. IE, grow
1585     // back quickly.
1586     //
1587     // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1588     // the available expansion space, whichever is smaller, as the base
1589     // expansion size. Then possibly scale this size according to how much the
1590     // threshold has (on average) been exceeded by. If the delta is small
1591     // (less than the StartScaleDownAt value), scale the size down linearly, but
1592     // not by less than MinScaleDownFactor. If the delta is large (greater than
1593     // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1594     // times the base size. The scaling will be linear in the range from
1595     // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1596     // ScaleUpRange sets the rate of scaling up.
1597     if (committed_bytes < InitialHeapSize / 4) {
1598       expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1599     } else {
1600       double const MinScaleDownFactor = 0.2;
1601       double const MaxScaleUpFactor = 2;
1602       double const StartScaleDownAt = _gc_overhead_perc;
1603       double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1604       double const ScaleUpRange = _gc_overhead_perc * 2.0;
1605 
1606       double ratio_delta;
1607       if (filled_history_buffer) {
1608         ratio_delta = recent_gc_overhead - threshold;
1609       } else {
1610         ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1611       }
1612 
1613       expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1614       if (ratio_delta < StartScaleDownAt) {
1615         scale_factor = ratio_delta / StartScaleDownAt;
1616         scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1617       } else if (ratio_delta > StartScaleUpAt) {
1618         scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1619         scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1620       }
1621     }
1622 
1623     log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1624                               "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1625                               recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1626 
1627     expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1628 
1629     // Ensure the expansion size is at least the minimum growth amount
1630     // and at most the remaining uncommitted byte size.
1631     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1632     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1633 
1634     clear_ratio_check_data();
1635   } else {
1636     // An expansion was not triggered. If we've started counting, increment
1637     // the number of checks we've made in the current window.  If we've
1638     // reached the end of the window without resizing, clear the counters to
1639     // start again the next time we see a ratio above the threshold.
1640     if (_ratio_over_threshold_count > 0) {
1641       _pauses_since_start++;
1642       if (_pauses_since_start > NumPrevPausesForHeuristics) {
1643         clear_ratio_check_data();
1644       }
1645     }
1646   }
1647 
1648   return expand_bytes;
1649 }
1650 
1651 void G1CollectorPolicy::print_tracing_info() const {
1652   _trace_young_gen_time_data.print();
1653   _trace_old_gen_time_data.print();
1654 }
1655 
1656 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1657 #ifndef PRODUCT
1658   _short_lived_surv_rate_group->print_surv_rate_summary();
1659   // add this call for any other surv rate groups
1660 #endif // PRODUCT
1661 }
1662 
1663 bool G1CollectorPolicy::is_young_list_full() const {
1664   uint young_list_length = _g1->young_list()->length();
1665   uint young_list_target_length = _young_list_target_length;
1666   return young_list_length >= young_list_target_length;
1667 }
1668 
1669 bool G1CollectorPolicy::can_expand_young_list() const {
1670   uint young_list_length = _g1->young_list()->length();
1671   uint young_list_max_length = _young_list_max_length;
1672   return young_list_length < young_list_max_length;
1673 }
1674 
1675 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1676   uint expansion_region_num = 0;
1677   if (GCLockerEdenExpansionPercent > 0) {
1678     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1679     double expansion_region_num_d = perc * (double) _young_list_target_length;
1680     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1681     // less than 1.0) we'll get 1.
1682     expansion_region_num = (uint) ceil(expansion_region_num_d);
1683   } else {
1684     assert(expansion_region_num == 0, "sanity");
1685   }
1686   _young_list_max_length = _young_list_target_length + expansion_region_num;
1687   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1688 }
1689 
1690 // Calculates survivor space parameters.
1691 void G1CollectorPolicy::update_survivors_policy() {
1692   double max_survivor_regions_d =
1693                  (double) _young_list_target_length / (double) SurvivorRatio;
1694   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1695   // smaller than 1.0) we'll get 1.
1696   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1697 
1698   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1699         HeapRegion::GrainWords * _max_survivor_regions, counters());
1700 }
1701 
1702 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1703   // We actually check whether we are marking here and not if we are in a
1704   // reclamation phase. This means that we will schedule a concurrent mark
1705   // even while we are still in the process of reclaiming memory.
1706   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1707   if (!during_cycle) {
1708     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1709     collector_state()->set_initiate_conc_mark_if_possible(true);
1710     return true;
1711   } else {
1712     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1713     return false;
1714   }
1715 }
1716 
1717 void G1CollectorPolicy::initiate_conc_mark() {
1718   collector_state()->set_during_initial_mark_pause(true);
1719   collector_state()->set_initiate_conc_mark_if_possible(false);
1720 }
1721 
1722 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1723   // We are about to decide on whether this pause will be an
1724   // initial-mark pause.
1725 
1726   // First, collector_state()->during_initial_mark_pause() should not be already set. We
1727   // will set it here if we have to. However, it should be cleared by
1728   // the end of the pause (it's only set for the duration of an
1729   // initial-mark pause).
1730   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1731 
1732   if (collector_state()->initiate_conc_mark_if_possible()) {
1733     // We had noticed on a previous pause that the heap occupancy has
1734     // gone over the initiating threshold and we should start a
1735     // concurrent marking cycle. So we might initiate one.
1736 
1737     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1738       // Initiate a new initial mark if there is no marking or reclamation going on.
1739       initiate_conc_mark();
1740       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1741     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1742       // Initiate a user requested initial mark. An initial mark must be young only
1743       // GC, so the collector state must be updated to reflect this.
1744       collector_state()->set_gcs_are_young(true);
1745       collector_state()->set_last_young_gc(false);
1746 
1747       abort_time_to_mixed_tracking();
1748       initiate_conc_mark();
1749       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1750     } else {
1751       // The concurrent marking thread is still finishing up the
1752       // previous cycle. If we start one right now the two cycles
1753       // overlap. In particular, the concurrent marking thread might
1754       // be in the process of clearing the next marking bitmap (which
1755       // we will use for the next cycle if we start one). Starting a
1756       // cycle now will be bad given that parts of the marking
1757       // information might get cleared by the marking thread. And we
1758       // cannot wait for the marking thread to finish the cycle as it
1759       // periodically yields while clearing the next marking bitmap
1760       // and, if it's in a yield point, it's waiting for us to
1761       // finish. So, at this point we will not start a cycle and we'll
1762       // let the concurrent marking thread complete the last one.
1763       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1764     }
1765   }
1766 }
1767 
1768 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1769   G1CollectedHeap* _g1h;
1770   CSetChooserParUpdater _cset_updater;
1771 
1772 public:
1773   ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1774                            uint chunk_size) :
1775     _g1h(G1CollectedHeap::heap()),
1776     _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1777 
1778   bool doHeapRegion(HeapRegion* r) {
1779     // Do we have any marking information for this region?
1780     if (r->is_marked()) {
1781       // We will skip any region that's currently used as an old GC
1782       // alloc region (we should not consider those for collection
1783       // before we fill them up).
1784       if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1785         _cset_updater.add_region(r);
1786       }
1787     }
1788     return false;
1789   }
1790 };
1791 
1792 class ParKnownGarbageTask: public AbstractGangTask {
1793   CollectionSetChooser* _hrSorted;
1794   uint _chunk_size;
1795   G1CollectedHeap* _g1;
1796   HeapRegionClaimer _hrclaimer;
1797 
1798 public:
1799   ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1800       AbstractGangTask("ParKnownGarbageTask"),
1801       _hrSorted(hrSorted), _chunk_size(chunk_size),
1802       _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1803 
1804   void work(uint worker_id) {
1805     ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1806     _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1807   }
1808 };
1809 
1810 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1811   assert(n_workers > 0, "Active gc workers should be greater than 0");
1812   const uint overpartition_factor = 4;
1813   const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1814   return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1815 }
1816 
1817 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1818   cset_chooser()->clear();
1819 
1820   WorkGang* workers = _g1->workers();
1821   uint n_workers = workers->active_workers();
1822 
1823   uint n_regions = _g1->num_regions();
1824   uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1825   cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1826   ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1827   workers->run_task(&par_known_garbage_task);
1828 
1829   cset_chooser()->sort_regions();
1830 
1831   double end_sec = os::elapsedTime();
1832   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1833   _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1834   _prev_collection_pause_end_ms += elapsed_time_ms;
1835 
1836   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1837 }
1838 
1839 // Add the heap region at the head of the non-incremental collection set
1840 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1841   assert(_inc_cset_build_state == Active, "Precondition");
1842   assert(hr->is_old(), "the region should be old");
1843 
1844   assert(!hr->in_collection_set(), "should not already be in the CSet");
1845   _g1->register_old_region_with_cset(hr);
1846   hr->set_next_in_collection_set(_collection_set);
1847   _collection_set = hr;
1848   _collection_set_bytes_used_before += hr->used();
1849   size_t rs_length = hr->rem_set()->occupied();
1850   _recorded_rs_lengths += rs_length;
1851   _old_cset_region_length += 1;
1852 }
1853 
1854 // Initialize the per-collection-set information
1855 void G1CollectorPolicy::start_incremental_cset_building() {
1856   assert(_inc_cset_build_state == Inactive, "Precondition");
1857 
1858   _inc_cset_head = NULL;
1859   _inc_cset_tail = NULL;
1860   _inc_cset_bytes_used_before = 0;
1861 
1862   _inc_cset_max_finger = 0;
1863   _inc_cset_recorded_rs_lengths = 0;
1864   _inc_cset_recorded_rs_lengths_diffs = 0;
1865   _inc_cset_predicted_elapsed_time_ms = 0.0;
1866   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1867   _inc_cset_build_state = Active;
1868 }
1869 
1870 void G1CollectorPolicy::finalize_incremental_cset_building() {
1871   assert(_inc_cset_build_state == Active, "Precondition");
1872   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1873 
1874   // The two "main" fields, _inc_cset_recorded_rs_lengths and
1875   // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1876   // that adds a new region to the CSet. Further updates by the
1877   // concurrent refinement thread that samples the young RSet lengths
1878   // are accumulated in the *_diffs fields. Here we add the diffs to
1879   // the "main" fields.
1880 
1881   if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1882     _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1883   } else {
1884     // This is defensive. The diff should in theory be always positive
1885     // as RSets can only grow between GCs. However, given that we
1886     // sample their size concurrently with other threads updating them
1887     // it's possible that we might get the wrong size back, which
1888     // could make the calculations somewhat inaccurate.
1889     size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1890     if (_inc_cset_recorded_rs_lengths >= diffs) {
1891       _inc_cset_recorded_rs_lengths -= diffs;
1892     } else {
1893       _inc_cset_recorded_rs_lengths = 0;
1894     }
1895   }
1896   _inc_cset_predicted_elapsed_time_ms +=
1897                                      _inc_cset_predicted_elapsed_time_ms_diffs;
1898 
1899   _inc_cset_recorded_rs_lengths_diffs = 0;
1900   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1901 }
1902 
1903 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1904   // This routine is used when:
1905   // * adding survivor regions to the incremental cset at the end of an
1906   //   evacuation pause,
1907   // * adding the current allocation region to the incremental cset
1908   //   when it is retired, and
1909   // * updating existing policy information for a region in the
1910   //   incremental cset via young list RSet sampling.
1911   // Therefore this routine may be called at a safepoint by the
1912   // VM thread, or in-between safepoints by mutator threads (when
1913   // retiring the current allocation region) or a concurrent
1914   // refine thread (RSet sampling).
1915 
1916   double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1917   size_t used_bytes = hr->used();
1918   _inc_cset_recorded_rs_lengths += rs_length;
1919   _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1920   _inc_cset_bytes_used_before += used_bytes;
1921 
1922   // Cache the values we have added to the aggregated information
1923   // in the heap region in case we have to remove this region from
1924   // the incremental collection set, or it is updated by the
1925   // rset sampling code
1926   hr->set_recorded_rs_length(rs_length);
1927   hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1928 }
1929 
1930 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1931                                                      size_t new_rs_length) {
1932   // Update the CSet information that is dependent on the new RS length
1933   assert(hr->is_young(), "Precondition");
1934   assert(!SafepointSynchronize::is_at_safepoint(),
1935                                                "should not be at a safepoint");
1936 
1937   // We could have updated _inc_cset_recorded_rs_lengths and
1938   // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1939   // that atomically, as this code is executed by a concurrent
1940   // refinement thread, potentially concurrently with a mutator thread
1941   // allocating a new region and also updating the same fields. To
1942   // avoid the atomic operations we accumulate these updates on two
1943   // separate fields (*_diffs) and we'll just add them to the "main"
1944   // fields at the start of a GC.
1945 
1946   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1947   ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1948   _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1949 
1950   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1951   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1952   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1953   _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1954 
1955   hr->set_recorded_rs_length(new_rs_length);
1956   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1957 }
1958 
1959 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1960   assert(hr->is_young(), "invariant");
1961   assert(hr->young_index_in_cset() > -1, "should have already been set");
1962   assert(_inc_cset_build_state == Active, "Precondition");
1963 
1964   // We need to clear and set the cached recorded/cached collection set
1965   // information in the heap region here (before the region gets added
1966   // to the collection set). An individual heap region's cached values
1967   // are calculated, aggregated with the policy collection set info,
1968   // and cached in the heap region here (initially) and (subsequently)
1969   // by the Young List sampling code.
1970 
1971   size_t rs_length = hr->rem_set()->occupied();
1972   add_to_incremental_cset_info(hr, rs_length);
1973 
1974   HeapWord* hr_end = hr->end();
1975   _inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
1976 
1977   assert(!hr->in_collection_set(), "invariant");
1978   _g1->register_young_region_with_cset(hr);
1979   assert(hr->next_in_collection_set() == NULL, "invariant");
1980 }
1981 
1982 // Add the region at the RHS of the incremental cset
1983 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1984   // We should only ever be appending survivors at the end of a pause
1985   assert(hr->is_survivor(), "Logic");
1986 
1987   // Do the 'common' stuff
1988   add_region_to_incremental_cset_common(hr);
1989 
1990   // Now add the region at the right hand side
1991   if (_inc_cset_tail == NULL) {
1992     assert(_inc_cset_head == NULL, "invariant");
1993     _inc_cset_head = hr;
1994   } else {
1995     _inc_cset_tail->set_next_in_collection_set(hr);
1996   }
1997   _inc_cset_tail = hr;
1998 }
1999 
2000 // Add the region to the LHS of the incremental cset
2001 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
2002   // Survivors should be added to the RHS at the end of a pause
2003   assert(hr->is_eden(), "Logic");
2004 
2005   // Do the 'common' stuff
2006   add_region_to_incremental_cset_common(hr);
2007 
2008   // Add the region at the left hand side
2009   hr->set_next_in_collection_set(_inc_cset_head);
2010   if (_inc_cset_head == NULL) {
2011     assert(_inc_cset_tail == NULL, "Invariant");
2012     _inc_cset_tail = hr;
2013   }
2014   _inc_cset_head = hr;
2015 }
2016 
2017 #ifndef PRODUCT
2018 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
2019   assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
2020 
2021   st->print_cr("\nCollection_set:");
2022   HeapRegion* csr = list_head;
2023   while (csr != NULL) {
2024     HeapRegion* next = csr->next_in_collection_set();
2025     assert(csr->in_collection_set(), "bad CS");
2026     st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
2027                  HR_FORMAT_PARAMS(csr),
2028                  p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
2029                  csr->age_in_surv_rate_group_cond());
2030     csr = next;
2031   }
2032 }
2033 #endif // !PRODUCT
2034 
2035 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
2036   // Returns the given amount of reclaimable bytes (that represents
2037   // the amount of reclaimable space still to be collected) as a
2038   // percentage of the current heap capacity.
2039   size_t capacity_bytes = _g1->capacity();
2040   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
2041 }
2042 
2043 void G1CollectorPolicy::maybe_start_marking() {
2044   if (need_to_start_conc_mark("end of GC")) {
2045     // Note: this might have already been set, if during the last
2046     // pause we decided to start a cycle but at the beginning of
2047     // this pause we decided to postpone it. That's OK.
2048     collector_state()->set_initiate_conc_mark_if_possible(true);
2049   }
2050 }
2051 
2052 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
2053   assert(!collector_state()->full_collection(), "must be");
2054   if (collector_state()->during_initial_mark_pause()) {
2055     assert(collector_state()->last_gc_was_young(), "must be");
2056     assert(!collector_state()->last_young_gc(), "must be");
2057     return InitialMarkGC;
2058   } else if (collector_state()->last_young_gc()) {
2059     assert(!collector_state()->during_initial_mark_pause(), "must be");
2060     assert(collector_state()->last_gc_was_young(), "must be");
2061     return LastYoungGC;
2062   } else if (!collector_state()->last_gc_was_young()) {
2063     assert(!collector_state()->during_initial_mark_pause(), "must be");
2064     assert(!collector_state()->last_young_gc(), "must be");
2065     return MixedGC;
2066   } else {
2067     assert(collector_state()->last_gc_was_young(), "must be");
2068     assert(!collector_state()->during_initial_mark_pause(), "must be");
2069     assert(!collector_state()->last_young_gc(), "must be");
2070     return YoungOnlyGC;
2071   }
2072 }
2073 
2074 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
2075   // Manage the MMU tracker. For some reason it ignores Full GCs.
2076   if (kind != FullGC) {
2077     _mmu_tracker->add_pause(start, end);
2078   }
2079   // Manage the mutator time tracking from initial mark to first mixed gc.
2080   switch (kind) {
2081     case FullGC:
2082       abort_time_to_mixed_tracking();
2083       break;
2084     case Cleanup:
2085     case Remark:
2086     case YoungOnlyGC:
2087     case LastYoungGC:
2088       _initial_mark_to_mixed.add_pause(end - start);
2089       break;
2090     case InitialMarkGC:
2091       _initial_mark_to_mixed.record_initial_mark_end(end);
2092       break;
2093     case MixedGC:
2094       _initial_mark_to_mixed.record_mixed_gc_start(start);
2095       break;
2096     default:
2097       ShouldNotReachHere();
2098   }
2099 }
2100 
2101 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
2102   _initial_mark_to_mixed.reset();
2103 }
2104 
2105 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
2106                                                 const char* false_action_str) const {
2107   if (cset_chooser()->is_empty()) {
2108     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
2109     return false;
2110   }
2111 
2112   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
2113   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2114   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2115   double threshold = (double) G1HeapWastePercent;
2116   if (reclaimable_perc <= threshold) {
2117     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2118                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2119     return false;
2120   }
2121   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2122                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2123   return true;
2124 }
2125 
2126 uint G1CollectorPolicy::calc_min_old_cset_length() const {
2127   // The min old CSet region bound is based on the maximum desired
2128   // number of mixed GCs after a cycle. I.e., even if some old regions
2129   // look expensive, we should add them to the CSet anyway to make
2130   // sure we go through the available old regions in no more than the
2131   // maximum desired number of mixed GCs.
2132   //
2133   // The calculation is based on the number of marked regions we added
2134   // to the CSet chooser in the first place, not how many remain, so
2135   // that the result is the same during all mixed GCs that follow a cycle.
2136 
2137   const size_t region_num = (size_t) cset_chooser()->length();
2138   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
2139   size_t result = region_num / gc_num;
2140   // emulate ceiling
2141   if (result * gc_num < region_num) {
2142     result += 1;
2143   }
2144   return (uint) result;
2145 }
2146 
2147 uint G1CollectorPolicy::calc_max_old_cset_length() const {
2148   // The max old CSet region bound is based on the threshold expressed
2149   // as a percentage of the heap size. I.e., it should bound the
2150   // number of old regions added to the CSet irrespective of how many
2151   // of them are available.
2152 
2153   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
2154   const size_t region_num = g1h->num_regions();
2155   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
2156   size_t result = region_num * perc / 100;
2157   // emulate ceiling
2158   if (100 * result < region_num * perc) {
2159     result += 1;
2160   }
2161   return (uint) result;
2162 }
2163 
2164 
2165 double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) {
2166   double young_start_time_sec = os::elapsedTime();
2167 
2168   YoungList* young_list = _g1->young_list();
2169   finalize_incremental_cset_building();
2170 
2171   guarantee(target_pause_time_ms > 0.0,
2172             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
2173   guarantee(_collection_set == NULL, "Precondition");
2174 
2175   double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
2176   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
2177 
2178   log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
2179                             _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
2180 
2181   collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
2182 
2183   if (collector_state()->last_gc_was_young()) {
2184     _trace_young_gen_time_data.increment_young_collection_count();
2185   } else {
2186     _trace_young_gen_time_data.increment_mixed_collection_count();
2187   }
2188 
2189   // The young list is laid with the survivor regions from the previous
2190   // pause are appended to the RHS of the young list, i.e.
2191   //   [Newly Young Regions ++ Survivors from last pause].
2192 
2193   uint survivor_region_length = young_list->survivor_length();
2194   uint eden_region_length = young_list->eden_length();
2195   init_cset_region_lengths(eden_region_length, survivor_region_length);
2196 
2197   HeapRegion* hr = young_list->first_survivor_region();
2198   while (hr != NULL) {
2199     assert(hr->is_survivor(), "badly formed young list");
2200     // There is a convention that all the young regions in the CSet
2201     // are tagged as "eden", so we do this for the survivors here. We
2202     // use the special set_eden_pre_gc() as it doesn't check that the
2203     // region is free (which is not the case here).
2204     hr->set_eden_pre_gc();
2205     hr = hr->get_next_young_region();
2206   }
2207 
2208   // Clear the fields that point to the survivor list - they are all young now.
2209   young_list->clear_survivors();
2210 
2211   _collection_set = _inc_cset_head;
2212   _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
2213   time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0);
2214 
2215   log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
2216                             eden_region_length, survivor_region_length, _inc_cset_predicted_elapsed_time_ms, target_pause_time_ms);
2217 
2218   // The number of recorded young regions is the incremental
2219   // collection set's current size
2220   set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
2221 
2222   double young_end_time_sec = os::elapsedTime();
2223   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
2224 
2225   return time_remaining_ms;
2226 }
2227 
2228 void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) {
2229   double non_young_start_time_sec = os::elapsedTime();
2230   double predicted_old_time_ms = 0.0;
2231 
2232 
2233   if (!collector_state()->gcs_are_young()) {
2234     cset_chooser()->verify();
2235     const uint min_old_cset_length = calc_min_old_cset_length();
2236     const uint max_old_cset_length = calc_max_old_cset_length();
2237 
2238     uint expensive_region_num = 0;
2239     bool check_time_remaining = adaptive_young_list_length();
2240 
2241     HeapRegion* hr = cset_chooser()->peek();
2242     while (hr != NULL) {
2243       if (old_cset_region_length() >= max_old_cset_length) {
2244         // Added maximum number of old regions to the CSet.
2245         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
2246                                   old_cset_region_length(), max_old_cset_length);
2247         break;
2248       }
2249 
2250 
2251       // Stop adding regions if the remaining reclaimable space is
2252       // not above G1HeapWastePercent.
2253       size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2254       double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2255       double threshold = (double) G1HeapWastePercent;
2256       if (reclaimable_perc <= threshold) {
2257         // We've added enough old regions that the amount of uncollected
2258         // reclaimable space is at or below the waste threshold. Stop
2259         // adding old regions to the CSet.
2260         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
2261                                   "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
2262                                   old_cset_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2263         break;
2264       }
2265 
2266       double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
2267       if (check_time_remaining) {
2268         if (predicted_time_ms > time_remaining_ms) {
2269           // Too expensive for the current CSet.
2270 
2271           if (old_cset_region_length() >= min_old_cset_length) {
2272             // We have added the minimum number of old regions to the CSet,
2273             // we are done with this CSet.
2274             log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
2275                                       "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
2276                                       predicted_time_ms, time_remaining_ms, old_cset_region_length(), min_old_cset_length);
2277             break;
2278           }
2279 
2280           // We'll add it anyway given that we haven't reached the
2281           // minimum number of old regions.
2282           expensive_region_num += 1;
2283         }
2284       } else {
2285         if (old_cset_region_length() >= min_old_cset_length) {
2286           // In the non-auto-tuning case, we'll finish adding regions
2287           // to the CSet if we reach the minimum.
2288 
2289           log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
2290                                     old_cset_region_length(), min_old_cset_length);
2291           break;
2292         }
2293       }
2294 
2295       // We will add this region to the CSet.
2296       time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
2297       predicted_old_time_ms += predicted_time_ms;
2298       cset_chooser()->pop(); // already have region via peek()
2299       _g1->old_set_remove(hr);
2300       add_old_region_to_cset(hr);
2301 
2302       hr = cset_chooser()->peek();
2303     }
2304     if (hr == NULL) {
2305       log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
2306     }
2307 
2308     if (expensive_region_num > 0) {
2309       // We print the information once here at the end, predicated on
2310       // whether we added any apparently expensive regions or not, to
2311       // avoid generating output per region.
2312       log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
2313                                 "old %u regions, expensive: %u regions, min %u regions, remaining time: %1.2fms",
2314                                 old_cset_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
2315     }
2316 
2317     cset_chooser()->verify();
2318   }
2319 
2320   stop_incremental_cset_building();
2321 
2322   log_debug(gc, ergo, cset)("Finish choosing CSet. old %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
2323                             old_cset_region_length(), predicted_old_time_ms, time_remaining_ms);
2324 
2325   double non_young_end_time_sec = os::elapsedTime();
2326   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2327 }
2328 
2329 void TraceYoungGenTimeData::record_start_collection(double time_to_stop_the_world_ms) {
2330   if(TraceYoungGenTime) {
2331     _all_stop_world_times_ms.add(time_to_stop_the_world_ms);
2332   }
2333 }
2334 
2335 void TraceYoungGenTimeData::record_yield_time(double yield_time_ms) {
2336   if(TraceYoungGenTime) {
2337     _all_yield_times_ms.add(yield_time_ms);
2338   }
2339 }
2340 
2341 void TraceYoungGenTimeData::record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times) {
2342   if(TraceYoungGenTime) {
2343     _total.add(pause_time_ms);
2344     _other.add(pause_time_ms - phase_times->accounted_time_ms());
2345     _root_region_scan_wait.add(phase_times->root_region_scan_wait_time_ms());
2346     _parallel.add(phase_times->cur_collection_par_time_ms());
2347     _ext_root_scan.add(phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan));
2348     _satb_filtering.add(phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering));
2349     _update_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS));
2350     _scan_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::ScanRS));
2351     _obj_copy.add(phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy));
2352     _termination.add(phase_times->average_time_ms(G1GCPhaseTimes::Termination));
2353 
2354     double parallel_known_time = phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan) +
2355       phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering) +
2356       phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS) +
2357       phase_times->average_time_ms(G1GCPhaseTimes::ScanRS) +
2358       phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy) +
2359       phase_times->average_time_ms(G1GCPhaseTimes::Termination);
2360 
2361     double parallel_other_time = phase_times->cur_collection_par_time_ms() - parallel_known_time;
2362     _parallel_other.add(parallel_other_time);
2363     _clear_ct.add(phase_times->cur_clear_ct_time_ms());
2364   }
2365 }
2366 
2367 void TraceYoungGenTimeData::increment_young_collection_count() {
2368   if(TraceYoungGenTime) {
2369     ++_young_pause_num;
2370   }
2371 }
2372 
2373 void TraceYoungGenTimeData::increment_mixed_collection_count() {
2374   if(TraceYoungGenTime) {
2375     ++_mixed_pause_num;
2376   }
2377 }
2378 
2379 void TraceYoungGenTimeData::print_summary(const char* str,
2380                                           const NumberSeq* seq) const {
2381   double sum = seq->sum();
2382   tty->print_cr("%-27s = %8.2lf s (avg = %8.2lf ms)",
2383                 str, sum / 1000.0, seq->avg());
2384 }
2385 
2386 void TraceYoungGenTimeData::print_summary_sd(const char* str,
2387                                              const NumberSeq* seq) const {
2388   print_summary(str, seq);
2389   tty->print_cr("%45s = %5d, std dev = %8.2lf ms, max = %8.2lf ms)",
2390                 "(num", seq->num(), seq->sd(), seq->maximum());
2391 }
2392 
2393 void TraceYoungGenTimeData::print() const {
2394   if (!TraceYoungGenTime) {
2395     return;
2396   }
2397 
2398   tty->print_cr("ALL PAUSES");
2399   print_summary_sd("   Total", &_total);
2400   tty->cr();
2401   tty->cr();
2402   tty->print_cr("   Young GC Pauses: %8d", _young_pause_num);
2403   tty->print_cr("   Mixed GC Pauses: %8d", _mixed_pause_num);
2404   tty->cr();
2405 
2406   tty->print_cr("EVACUATION PAUSES");
2407 
2408   if (_young_pause_num == 0 && _mixed_pause_num == 0) {
2409     tty->print_cr("none");
2410   } else {
2411     print_summary_sd("   Evacuation Pauses", &_total);
2412     print_summary("      Root Region Scan Wait", &_root_region_scan_wait);
2413     print_summary("      Parallel Time", &_parallel);
2414     print_summary("         Ext Root Scanning", &_ext_root_scan);
2415     print_summary("         SATB Filtering", &_satb_filtering);
2416     print_summary("         Update RS", &_update_rs);
2417     print_summary("         Scan RS", &_scan_rs);
2418     print_summary("         Object Copy", &_obj_copy);
2419     print_summary("         Termination", &_termination);
2420     print_summary("         Parallel Other", &_parallel_other);
2421     print_summary("      Clear CT", &_clear_ct);
2422     print_summary("      Other", &_other);
2423   }
2424   tty->cr();
2425 
2426   tty->print_cr("MISC");
2427   print_summary_sd("   Stop World", &_all_stop_world_times_ms);
2428   print_summary_sd("   Yields", &_all_yield_times_ms);
2429 }
2430 
2431 void TraceOldGenTimeData::record_full_collection(double full_gc_time_ms) {
2432   if (TraceOldGenTime) {
2433     _all_full_gc_times.add(full_gc_time_ms);
2434   }
2435 }
2436 
2437 void TraceOldGenTimeData::print() const {
2438   if (!TraceOldGenTime) {
2439     return;
2440   }
2441 
2442   if (_all_full_gc_times.num() > 0) {
2443     tty->print("\n%4d full_gcs: total time = %8.2f s",
2444       _all_full_gc_times.num(),
2445       _all_full_gc_times.sum() / 1000.0);
2446     tty->print_cr(" (avg = %8.2fms).", _all_full_gc_times.avg());
2447     tty->print_cr("                     [std. dev = %8.2f ms, max = %8.2f ms]",
2448       _all_full_gc_times.sd(),
2449       _all_full_gc_times.maximum());
2450   }
2451 }